Carpet reclamation process

ABSTRACT

A process for the reclamation of base materials from carpet is disclosed. The process includes contacting the carpet with a composition which contains a chemical softening agent for the binder material in the carpet and separating the carpet pile from the carpet backing(s).

This is a continuation-in-part of an International Application, SerialNo.: PCT/US 95/12186 having an international filing date of Sep. 26,1995 which is a continuation-in-part of a Canadian patent applicationSerial No 2,133,303 filed on Sep. 29, 1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to an improved process for carpetreclamation and more particularly, the process is directed to the use ofan agent for chemically softening or swelling binder materialconventionally associated with carpet in order to expedite and simplifythe reclamation process.

2. Description of the Prior Art

Carpet reclamation processes have been previously proposed in the artand are exemplified by the process disclosed in U.S. Pat. No. 5,230,473,issued to Hagguist et al., Jul. 27, 1993.

In the Hagguist et al. method, apart from introductory steps whichinvolve screening the carpet, and preliminary loop cutting and otherprocessing, the removal of the secondary backing involves a whole seriesof steps. This additionally is the situation when the binder material isto be removed from the primary backing.

In greater detail and with respect to the removal of the secondarybacking from the carpet, the carpet must be initially exposed to fluidsunder pressure for loosening and debonding the latex binder from thesecondary backing. The next step includes passing the remaining materialonto a further processing stage where the secondary backing ismechanically treated with rotating mechanical impingement devices onboth sides of the carpet. It is the mechanical arrangement that resultsin the removal of the secondary backing. At this time, the binder systemis still substantially intact.

In order to remove the binder material, the remaining carpet structuremust be passed to yet another stage where there is included a pluralityof rotating brushes as well as rotating high pressure nozzle heads.This, as indicated by the patentees, results in the gradual looseningand removal of the binder system from the primary backing.

In view of the teachings of this reference, it is clear that the methodis dependent on the use of mechanical means for the removal of not onlythe secondary backing, but further the removal of the latex binderconventionally positioned between the secondary backing and the primarybacking.

The Hagguist et al. process also suffers the drawbacks common to allmultiple step processes, including increased production time and cost,the use of a greater number of moving parts, the potential requirementfor a larger labor force and difficulty in efficiently operating at acommercial level wherein, for example, millions of square meters ofcarpet may be processed.

In view of what has been proposed in the prior art set forth above,there clearly exists a need for a high efficiency method of reclaimingbase components of a carpet quickly and without the use of toxiccontaminants or complex, multiple stage processes.

BRIEF SUMMARY OF THE INVENTION

The present invention satisfies the above needs and achieves the resultsand benefits set forth below by providing a process for reclaimingcarpet components, the carpet including backing material, bindermaterial and carpet pile. In a first embodiment, the process includesthe steps of: contacting the carpet with a composition including achemical softening agent (as defined below) for the binder andseparating the pile from the backing.

The amount of chemical softening agent in the composition and theconditions for the contacting step, for example temperature and time,may be selected to either substantially dissolve the binder or softenthe binder.

In a second embodiment, the process includes reducing the size of thecarpet to form a reduced carpet sample; combining at least a portion ofthe reduced carpet sample with a composition including a chemicalsoftening agent for the binder to form a carpet/composition mixture; andapplying to the mixture shear forces under turbulent conditions in anamount sufficient to promote detachment of the binder from the remainingmaterials (e.g., pile material and/or backing material).

The process and device of the present invention permits the reuse andrecycle of the pile or backing material into critical end uses requiringa high degree of product purity such as, for example, carpet fibers,plastic pellets and other materials. Once the contacting step iscomplete, the various materials may be further separated from each otherby making use of mechanical means, fluid means including air and liquidflow, vacuum means or by manual means.

According to yet another aspect of one embodiment of the presentinvention there is provided a system for reclaiming carpet components,the carpet including backing material, binding material and carpet pile,the system including: advancing means for advancing the carpet to asolvent application means; solvent application means for applyingsolvent to the carpet to dissolve the binder material; and collectionmeans for collecting separated backing material and carpet pile.

It will be readily appreciated that the process as set forth herein isclearly applicable to all carpet types including, for example, standardcarpet with styrene butadiene rubber latex binders and primary andsecondary backings, and those with foam layers, including urethanes.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the invention, reference will be madebelow to the accompanying drawings illustrating preferred embodimentsand in which:

FIGS. 1 and 2 illustrate various types of carpeting in cross-section;and

FIG. 3 is a schematic illustration of the process according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, FIGS. 1 and 2 illustrate cross-sectionalviews of typical carpet varieties which are processable according to thepresent invention. In FIG. 1, the carpet 10 includes a primary backing12 within which is disposed carpet pile 14. The carpet pile 14 isfixedly secured to backing 12 with binder 16, typically a latex binder.Preferably, a secondary backing 18 is additionally provided and issecured to primary backing 12 by binder 16.

FIG. 2 illustrates a second carpet type wherein the binder material 16comprises a foam material 20 and the carpet 10 does not include asecondary backing.

While these carpet types are shown as exemplary of carpets processableaccording to the present invention, it will be appreciated by thoseskilled in the art that other types of carpeting may also be processedaccording to the present invention.

Prior to the performance of the process of the present invention, thecarpet may be screened for processing suitability. The use of visualinspection, metal detectors, etc., may be employed to this end. Further,the carpet may be cleaned or preconditioned with, for example, a surfaceactive agent or other compound(s) to enhance the processing thereof.

A first embodiment of the process of the present invention includescontacting the carpet with a composition which includes a chemicalsoftening agent for the binder. The term “chemical softening agent”, asutilized herein, is defined as any agent capable under specifiedconditions of softening or swelling a material, for example, a bindermaterial, via chemical reaction or interaction therewith, for example,via interruption of the molecular forces in a polymeric matrix resultingin an opening of its structure. The specific chemical softening agentwill therefore be selected based on the type and nature of the binderused in the carpet. The term “composition” is defined herein to include,without limitation, mixtures, solutions, emulsions, dispersions and thelike.

The chemical softening agent preferably is non-toxic and environmentallyfriendly. A preferred chemical softening agent includes at least onedimethyl ester. Dimethyl adipate, dimethyl glutamate, dimethyl succinateand mixtures thereof are especially preferred. Particularly preferredchemical softening agents are dimethyl succinate and a mixture ofdimethyl adipate and dimethyl glutarate. Suitable dimethyl esters arecommercially available from Monsanto Company under the trade nameSANTOSOL®.

Suitable compositions include aqueous or non-aqueous compositions of thechemical softening agent. In order to further enhance the dissolution orsoftening of the binder, additional chemicals may be added to thecomposition including, for example, surface active agents to enhance thewettability of the backing material of the carpet. In addition,thickeners may be added to control the flow and adhesive properties ofthe composition. A particularly useful thickener is commerciallyavailable from B. F. Goodrich under the trade name CARBOPOL®.

A preferred composition includes at least one dimethyl ester and water,most preferably in a weight ratio of about 1:1.

The concentration of chemical softening agent in the composition willvary greatly depending on the type of carpet and the conditions utilizedin the contacting step such as, for example, time and temperature.Preferred chemical softening agent amounts are from at least about 10%by weight based on the total weight of the composition.

The contacting step may be performed by any method, including, forexample, immersing the carpet in the composition, applying thecomposition to the pile or applying the composition to the backing.Preferably, the contacting step is performed in the presence of asurface active agent. The surface active agent may be added to thecomposition which contacts the carpet or it may be pre-applied to thecarpet prior to the contacting step. Suitable surface active agentsinclude, for example, anionic and nonionic surfactants.

The condition for the contacting step will vary greatly depending on,for example, the carpet type, type and concentration of chemicalsoftening agent, and the like. Contact time will generally extend atleast 5 seconds while the contact temperature may range from ambienttemperatures to just below the boiling point of the composition. In apreferred embodiment wherein at least one dimethyl ester is utilized asthe chemical softening agent, the contacting step is performed at atemperature of at least 20° C., more preferably at least 35° C.

Preferably, the concentration of softening agent is selected and thecontacting step is performed under conditions sufficient to reduce theamount of force required to remove a tuft from the carpet by at least50% according to the test set forth in the examples below.

In a preferred embodiment, the concentration of chemical softening agentis selected and the contacting step is performed under conditionssufficient to soften the binder. In this embodiment, the process of thepresent invention optionally includes removing binder from the pileafter pile is separated from the backing.

Any residual composition present on the individual base components (pileand/or backing[s]) of the carpet may be removed by simply washing thecomponents and this may additionally include pressurized washing makinguse of a suitable washing agent.

A preferred method for removing the binder material from the pileincludes applying to the pile, preferably in the presence of thechemical softening agent, shear forces under turbulent conditions in anamount sufficient to detach the binder from the pile. It is to beunderstood that the amount of shear forces, the extent of the turbulenceand the time required to detach the binder from the pile will varydepending on a number of factors, for example, the conditions underwhich the contacting step is performed, the conditions under which theforce is applied, the strength of the attachment of the binder to thepile, and the type and composition of the binder.

In a second embodiment, the process of the present invention includesreducing the size of the carpet to form a reduced carpet material. Thephrase “reducing the size”, as utilized herein, is defined to includeany known methods for decreasing the size of the carpet and/or itscomponent parts to a size and form suitable for subsequent processing asset forth below. The reduced carpet material includes pile materialtypically with at least some binder material attached thereto and/orbacking material typically with at least some binder material attachedthereto.

This size reduction step can be suitably performed by any of the commonand commercially available attrition devices known to one of ordinaryskill in the art, for example cutters, shredders, fiberizers, wetattrition devices, hammer mills, particulate grinders, knife mills, andsimilar devices as well as combinations thereof. It will be understoodby one of ordinary skill in the art that, depending upon the specificmethods and devices utilized for this size reduction step, the resultingreduced carpet sample can but may not necessarily retain the structuralform of the original carpet.

In those situations where the carpet pile and the carpet backingmaterial are made from dissimilar polymeric materials, the processpreferably further includes, separating the reduced carpet material intoa first stream primarily including pile material and a second streamprimarily including backing material. Most preferably, this step isperformed prior to the combining step below such that both of thesestreams will contain at least some amount of binding entrained in thestream and/or attached to the stream's primary component. Thisseparation step can be suitably performed by any of the common andcommercially available mechanical separation devices known to one ofordinary skill in the art, for example cyclones, air separators,hydrocyclones, centrifuges, and similar devices or combinations thereof.

The next step includes combining at least a portion of the reducedcarpet material with a composition including a chemical softening agentfor the binder to form a carpet/composition mixture.

The chemical softening agent preferably is non-toxic and environmentallyfriendly. A preferred chemical softening agent includes at least onedimethyl ester. Dimethyl adipate, dimethyl glutamate, dimethyl succinateand mixtures thereof are especially preferred. Particularly preferredchemical softening agents are dimethyl succinate and a mixture ofdimethyl adipate and dimethyl glutarate. Suitable dimethyl esters arecommercially available from Monsanto Company under the trade nameSANTOSOL®.

Suitable compositions include aqueous or non-aqueous compositions of thechemical softening agent. In order to further enhance the dissolution orsoftening of the binder, additional chemicals may be added to thecomposition including, for example, surface active agents to enhance thewettability of the backing material of the carpet. In addition,thickeners may be added to control the flow and adhesive properties ofthe composition. A particularly useful thickener is commerciallyavailable from B. F. Goodrich under the trade name CARBOPOL®.

A preferred composition includes at least one dimethyl ester and water,most preferably in a weight ratio of about 1:1.

The concentration of chemical softening agent in the composition willvary greatly depending on the type of carpet and the conditions utilizedin the contacting step such as, for example, time and temperature.Preferred chemical softening agent amounts are from at least about 10%by weight based on the total weight of the composition.

The combining step may be performed by any method, including, forexample, immersing or mixing the ground carpet in the composition,soaking the ground carpet with the composition or applying thecomposition to the ground carpet by spray or similar means. Preferably,the combining step is performed in the presence of a surface activeagent. Suitable surface active agents include, for example, anionic andnonionic surfactants.

The condition for the combining step will vary greatly depending on, forexample, the carpet type, type and concentration of chemical softeningagent, and the like. Contact time will generally extend at least 5seconds while the contact temperature may range from ambienttemperatures to just below the boiling point of the composition. In apreferred embodiment wherein at least one dimethyl ester is utilized asthe chemical softening agent, the contacting step is performed at atemperature of at least 20° C., more preferably at least 35° C.

In a particularly preferred embodiment, the process includes applying toat least a portion of the carpet/composition mixture shear forces underturbulent conditions. The shear forces and turbulence are present in anamount sufficient to promote detachment of any binder attached to thetuft material and/or backing material. It is to be understood that theamount of shear forces and turbulence and the force application timerequired to detach the binder from the material will vary depending on anumber of factors, for example the conditions under which the combiningstep is performed, the conditions under which the force is applied, thestrength of the attachment of the binder, and the type and compositionof the binder.

Subsequent to the shear force application step, the treated carpetmaterial may be further processed. For example, the treated carpetmaterial may be washed or cleaned, preferably with water, lower alcoholssuch as methanol or mixtures thereof. Similarly, the composition mayalso be further processed, for example by purification or recoverythereof for reuse or by removal of the softened or swelled bindermaterial therefrom.

Turning to FIG. 3, which illustrates a schematic illustration of adevice suitable for practicing one embodiment of the process of theinvention for processing the carpet of FIG. 1, a first roller 30advances the carpet material to a first pair of liquid nip rollers 32and 34. First set of rollers 32 and 34 include the composition forapplication onto the secondary backing 18 of the carpet 10. Thecomposition is preferably heated such that the contacting step isconducted at a temperature of at least 35° C. A second set of rollers 36and 38 further apply additional amount of the composition through thesecondary backing into the binder material of the carpet.

The carpet is then passed between two star wheels 40 and 42 whichmechanically loosen the secondary backing from the carpet passingtherethrough. At this point, the secondary backing is effectivelyremoved from the carpet and to this end, an abrasive roll 44 is providedand further acts on a smooth roll 46 to remove the secondary backingfrom the carpet. The removed secondary backing may be passed on throughrollers 48 and 50 to a high pressure wash, globally denoted by numeral52, optionally dried by pressure rollers 54 and 56 and collected on aspool 58 for subsequent usage.

Once the secondary backing 18 has been completely removed, the primarybacking 12, together with the pile 14 and binder 16, are further treatedwith the solvent using a nip roller arrangement 60 and 62 in a similarmanner as set forth with respect to nips 32 and 34. After a suitabledwell time, the remaining material is subjected to a high pressure waterwash at 64 in order to remove any residual binder from the primarybacking along with any remaining solvent. After entering the washingcycle 64, the primary backing and carpet pile is then dried in a dryingcycle at 66 using any suitable means for effectively drying, e.g. forcedhot air.

In order to remove the carpet pile 14 from the primary backing 12, oncedried, the primary backing and carpet pile are passed into contact overa source of vacuum. In the embodiment shown, this is an inverted vacuumplate 68 which pulls the carpet pile 14 of the primary backing 12 forsubsequent collection as generally indicated by the arrow 70 in FIG. 3.Any remaining particles of binder 16 are then dropped into a collectionunit (not shown). The separated primary backing 12 is then optionallywashed and passed on to a collection spool, the latter steps not beingschematically illustrated in FIG. 3.

As further steps, the composition may be applied pressurably to thecarpet. Further, the carpet may be passed through the system a secondtime, when required.

In addition to the above, the spent composition may be reused byrecycling the same subsequent to filtering the spent composition.Further, the composition may be purified by distillation or otherwell-known chemical purification techniques.

Other materials may be combined with the composition to enhancesoftening or swelling of the binder.

The following examples, while not intended to limit the scope of thepresent invention, serve to further illustrate and describe itsbenefits.

EXAMPLES 1-9

I. Composition Preparation

Compositions for use in the process of the present invention wereformulated according to the specifications set forth in Table 1 below.

TABLE 1 Compositions Chemical Softening Agent Wt % of Water Item No.Composition Wt % of Composition 1 dimethyl adipate, 100% 0% 2 dimethyladipate, 50% 50% 3 dimethyl succinate, 100% 0% 4 dimethyl succinate, 50%50% 5 dimethyl glutarate, 100% 0% 6 dimethyl glutarate, 50% 50% 7dimethyl adipate, 23-27% 0% dimethyl glutarate, 72-76% 8 dimethyladipate, 12-14% 50% dimethyl glutamate, 36-38%

II. Carpet Treatment Procedure

2-inch (5.08 cm) by 2-inch (5.08 cm) samples of a conventional carpetconstruction having tufts, a primary backing, a styrene-butadiene rubberlatex adhesive and a secondary backing were partially immersed in one ofthe composition items in Table 1 at ambient temperature. For eachcomposition item, the composition amounts tested were 5 ml, 7 ml and 10ml. For each amount tested, the immersion times tested were 5 minutes,60 minutes and 18 hours. Control samples were left untreated.

II. Tuft Removal Test

The samples, including the controls, were then tested to determine theforce required to remove a tuft from the sample. Each sample wasimmobilized and any excess composition removed. The tip of an individualtuft was then grasped with a clamp and pulled on until it was removedfrom the carpet sample without breaking. The clamp was connected to aconventional INSTRON® testing device which measured the maximum pullingforce exerted on the tuft by the clamp during its removal from thecarpet sample. Three individual tufts from each sample were tested inthis manner and an arithmetic average force (F) for each sample wascalculated. A force reduction percentage versus the control was alsocalculated as

%ΔF=[(F_(control)−F)/F_(control)]×100%

The results are set forth below in Table 2, with item numberscorresponding to those provided in Table 1.

TABLE 2 Force Reduction % Item No. (% ΔF from Control) 1 67.8 2 75.0 357.1 4 78.6 5 57.1 6 78.6 7 71.4 8 78.6 Control 0 (Untreated Samples)

As shown above, the process of the present invention reduced the forcerequired for tuft removal at least 50% and for some items as much as 75%or more.

EXAMPLES 10-14

For examples 10-14, compositional items 2, 4, 6, and 8 from Table 1 wereutilized in test procedures identical to those set forth in Examples 1-9except that the treatment of the carpet sample was conducted at atemperature of 50° C. The results are set forth below in Table 3.

TABLE 3 Composition % ΔF from Test Item No. Item No. Control 10 2 82.111 4 89.3 12 6 85.7 13 8 78.6 14 Control 0 (Untreated Samples)

As shown above, the presence of heat in the contacting step of theprocess of the present invention further reduces the force required fortuft removal.

EXAMPLE 15

A carpet sample of nylon 6,6 pile, polypropylene primary and secondarybackings and styrene butadiene rubber (SBR)-based binder (75% calciumcarbonate, 25% SBR) was procured. The sample was converted into areduced carpet material by simple cutting of the larger carpet intosmall pieces which varied in size and shape but which had an approximateaverage size of about one square inch. As the goal of this particularprocedure was to obtain 99.9%+ pure nylon 6,6, the nylon 6,6 pilematerial (tufts) was separated from the reduced carpet material forfurther processing (sample #1). The portion of the pile material whichincluded binder attached thereto was then separated from the remainingpile material by cutting (sample #2). By visual inspection, thisbinder-encrusted pile material included about 50% pile and 50% encrustedbinder. The combining step was then performed by adding about 10 g ofthe encrusted pile material to about 500 ml of a dimethyl ester mixtureincluding dimethyl adipate, dimethyl glutarate and dimethyl succinateheated to 85° C. Shear forces are then applied to thecomposition/material mixture under turbulent conditions for five minutesutilizing a commercially available blending device (WARING®) set at highspeed.

The composition was then drained off to obtain a wet mass of the pilematerial (sample #3). This wet mass was dried at an elevated temperatureand washed with a methanol.

The various materials obtained throughout this process, identified aboveas numbered samples, were then analyzed for binder content by an ashtest wherein the nylon was subjected to a temperature of about 800° C.for one hour and the amount of remaining calcium carbonate converted tocalcium oxide was measured. Ash content for the various materials wasmeasured as shown in Table 4 below.

TABLE 4 % Material Description % Ash CaCO₃ % SBR* 1 Uncut Pile Materialwith 14.0 24.84 8.28 Latex 2 Cut Pile Material with Latex 28.0 49.8216.61 3 Treated, Unwashed Pile 0.14 0.11 0.04 Material 4 Treated, WashedPile 0.08 0 0 Material *This calculation assumes a pile TiO₂concentration of 0.08% by weight. Higher TiO₂ concentrations in thepile, while possible, would lower the calculated % SBR value. The exact% SBR value may actually be lower and the value provided is therefore amaximum for that sample.

Some of the processed pile material was also inspected under ahigh-power microscope for the presence of the SBR. The results of thevisual inspection correlated with the results of the ash test above.

From these results, it will be clear to one of ordinary skill in the artthat the present process is particularly useful for recovery of highpurity (99%+) pile material from carpet.

Although embodiments of the invention have been described in detailherein, it will be appreciated by those skilled in the art that numerousmodifications may be made invention without departing from the intendedscope of the invention.

We claim:
 1. A process for reclaiming carpet components, said carpetincluding a backing and carpet pile disposed within said backing andsecured to said backing with a binder, said process comprising: (a)reducing the size of said carpet to form a reduced carpet materialincluding pile material, backing material and binder material attachedto at least one of said pile material and backing material; (b)combining at least a portion of the reduced carpet material with acomposition including a chemical softening agent for the binder to forma mixture; and (c) applying to the mixture shear forces under turbulentconditions in an amount sufficient to promote detachment of the binderfrom at least one of said pile material and said backing material. 2.The process of claim 1 further including separating said reduced carpetmaterials into a first stream comprising primarily pile material and asecond stream comprising primarily backing material.
 3. The process ofclaim 2 wherein said separating step is performed prior to saidcombining step.
 4. The process of claim 1 wherein said chemicalsoftening agent comprises at least one dimethyl ester.
 5. The process ofclaim 4 wherein said dimethyl ester is selected from the groupconsisting of dimethyl adipate, dimethyl glutarate, dimethyl succinate,and mixtures thereof.
 6. The process of claim 4 wherein said compositionfurther comprises water.
 7. The process of claim 6 wherein saidcontacting step is conducted at a temperature of at least 35° C.